The invention relates to a shock dampener bumper for motor-vehicles, adapted to be applied on to motor-vehicles of various kind, both for personal uses and for sports contests and made in a simple, practical and versatile manner, in order to prevent damages to the motor-vehicle constructive structure in cases in which they fall, by dampening effectively the shocks deriving from the contact with the ground. Shock dampener bumpers built in on the motor-vehicles of the kind referred to are known, for dampening shocks deriving when such motor-vehicles fall on to the ground, in a way to avoid or limit as much as possible the damages to the constructive structure of the same motor-vehicles. These bumpers are generally constituted by a single adequately shaped part of aluminium or plastic material, which is secured at its one end portion laterally on a suitable position to the motor-vehicle constructive structure, by utilizing suitable thickening elements and screws, and the other free end portion of which is slightly projected from the profile of the relative motor-vehicle constructive structure and, during the fall, comes into contact with the ground by damping such shocks, thereby preventing that such constructive structure comes into contact with the ground, by damaging or breaking it. These kinds of bumpers provide for effective damping actions which depend on the their size and the composition of their material, in that during the impact with the ground they transmit unavoidably some vibrations to the constructive structure of the relative motor-vehicle too, and these vibrations are absorbed effectively by the material of the same bumpers, and therefore do not produce damages to such structure, until the bumpers have pre-established sizes. On the contrary, in the case in which such bumpers have sizes greater than such pre-established values, the vibrations produced when the motor-vehicle falls exceed the safety values and may also be amplified, and under such circumstances when impacting the ground the bumper behaves like a component integral with the motor-vehicle constructive structure, in such a manner to safeguard only the more external parts of the constructive structure, by discharging through the bumper securing support all the energy deriving by the impact of both such support and the remaining component parts of the structure (engine, etc.), thereby producing the breaking and damaging of all these parts.